GUANIDINE AND ITS DERIVATIVES 165 



Methyl Guanidine and Dimethyl Guanidine. 



/NH.CH, /NH.CH-, 



C NH C NH 



Methyl guanidine has been isolated from meat and meat extracts, in which 

 about i per cent, is present. It has also been isolated from urine.' 

 Dimethyl guanidine has been isolated from urine. 

 Methyl guanidine is probably derived from creatine. 



NH 2 NH 2 



Arginine. NH=C NH . cu^ . CH 2 . CH 2 . CH . COOH. ' 

 Arginine, or S-guanidine-tf-aminovalerianic acid is a constituent 

 of the protein molecule ; in some proteins the protamines it forms 

 over 80 per cent of the molecule (p. 432). It was discovered in ex- 

 tracts of seedlings. 



Preparation. 



Arginine is most easily prepared by the hydrolysis of edestin, the 

 protein of hemp seed, 1 or from seedlings of the yellow lupin. 2 Its con- 

 stitution was proved by its synthesis from cyanamide and ornithine : 

 NH 2 NH 2 



CN +H 2 N^CH 2 CH 2 CH 2 CH^ 

 NH 2 NH 2 



NH C NH CH 2 CH 2 CH 2 CH COOH. 



Properties and Reactions. 



Arginine is a white crystalline substance, easily soluble in water, 

 but insoluble in alcohol. It melts with decomposition at 207-5. It 

 is a strong base and absorbs carbon dioxide from the air forming 

 arginine carbonate. It also forms salts with other acids, of which the 

 nitrate is the principal one. 



Natural arginine is optically active, the synthetical product is 

 optically inactive but has been separated into its stereoisomers. 



Like guanidine it is hydrolysed by alkalies into urea and ornithine : 

 NH 2 NH 2 



NH=rC NH . CH 2 . CH 2 . CH 2 . CH . COOH + H 2 O = 

 NH 2 NH 2 



NH 2 C O + NH 2 . CH 2 . CH 2 . CH 2 . CH . COOH. 



This hydrolysis of arginine occurs in the liver by the action of the 

 enzyme arginase. A portion of the urea in the urine is probably 

 derived in this way. 



J 



Ber., 1905, 38, 4187. 

 2 See Zeit. Physiol. Chem., 1902, 35, 314. 



